<md-toolbar color="primary">
  <div *ngIf="user">{{user.email}}</div>
  <button md-button (click)="signIntoGithub()" *ngIf="!user">Sign In with Github</button>
  <button md-button (click)="signOutFromGithub()" *ngIf="user">Sign out</button>
</md-toolbar>

